The foundation of a wind turbine tower, either it is of the onshore or the offshore type, must have sufficient strength to withstand extreme loads with a suitable margin of safety. This is especially relevant when the tower is very high and blades are required to be considerably long, especially when high power is to be generated by the wind turbine.
In this respect, the foundation of a wind turbine tower must be also designed to withstand fatigue damage due to operational loads and to certain conditions such as nacelle yawing, start-ups and shutdowns, etc.
For this purpose, the dimensions of the foundation upon which the wind turbine is supported are increased according to the requirements. Increased dimensions result in a number of disadvantages. These disadvantages are related, for example, to increased manufacturing and transportation costs.
Document WO2004101898A2 provides a circular foundation formed of a number of parts, namely a central hollow-cylindrical base and a plurality of radially extending foot modules. The foot modules can be transported separately to the site where the wind turbine is to be erected. However, the cylindrical base of the foundation is made of a single piece and it is very large such that transportation of wind turbine parts in this case remains a complex operation and costs remain undesirably increased.
U.S. 2010024311 discloses a wind turbine tower having a tubular tower mount made of a continuous piece for supporting the tower one end of which can be connected to the tower and the other end being mountable on a foundation. The tower mount cross-section is greater than its height and includes a plurality of circumferential segments that are connectable to each other to form the tubular tower mount. In this case, the provision of a tower mount made of a continuous piece allows stress concentration in the joining areas of the circumferential segments.